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- Title
Is the Carhart notch a predictive factor of hearing results after stapedectomy ?
- Authors
Schmerber, S.; Lamblin, E.; Baguant, A.; Quatre, R.
- Abstract
Objective: The Carhart notch (CN) is a depression in the bone-conduction audiogram of patients with clinical otosclerosis, maximal at 2 kHz. The middle frequencies from 0.5 to 2 kHz, which correspond to the resonance frequency of the middle ear, can be substantially improved following successful stapes surgery. However, definite criteria for the detection of a CN remain unclear. The main goal of our study was to determine whether preoperative audiological assessment as the presence of a CN were predictive factors for postoperative hearing results such as BC threshold improvement. Method: Retrospective audiometric database and chart review in one tertiary referral center performed with the aim of assessing whether the presence of a CN could be predictive of results after stapes surgery in otosclerosis, through improvement in BC thresholds. An assessment of hearing status was performed before and after surgery at 4 months and at 1 year. We used a 4-frequency pure-tone average for AC and BC thresholds (0.5, 1, 2, and 4 kHz). Only AC and BC results that were obtained at the same time postoperatively were used for calculation of the postoperative air-bone gap (ABG). BC threshold improvement, i.e. overclosure, was measured by the preoperative minus the postoperative pure-tone BC average. Audiometry was assessed according to the American Academy of Otolaryngology Head and Neck Surgery guidelines except for thresholds at 3 kHz which were substituted in all cases with those at 4 kHz. This was necessary because 3 kHz measurements were not performed at the beginning of this study. Material: Nine hundred and thirty-one cases of stapes surgery over a period of 25 years benefitted from an audiological assessment before and 4 months after surgery. A CN was considered present when the BC threshold at the notch frequency (0.5, 1 or 2 kHz) exceeded the mean thresholds at higher and lower adjacent frequencies by at least 7.5 dB. BC threshold improvement was better at 2 kHz (+14.1±12.5 dB vs. +12±13.2 dB) and lower at 4 kHz (+3.6±13.5 dB vs. +11±14.7 dB) for the CN+ group compared to the CN-- group. Moreover, sensorineural hearing loss was more frequent in the CN+ group than in the CN-- group. Results: A CN was observed in 495 (53.1%) of the 931 surgical cases in the preoperative audiogram according to our definition. Notches were distributed according to the peak frequency as follows: 273 (29.2%) surgical cases at 2 kHz, 44 (4.7%) at 1 kHz, and 178 (19.1%) at 0.5 kHz. The CN depth means (corresponding to the difference of mean adjacent thresholds minus CN threshold) were: 13 ± 4.7 dB for 2 kHz CN, 11.3±4.4 dB for 1 kHz CN, and 11.5±4.7 dB for 0.5 kHz CN. Improvement of BC thresholds 4 months after surgery were significantly different if a CN was observed on preoperative audiogram (495 cases with CN: CN+ group) or not (436 cases without CN: CN-- group). BC thresholds improvement for the CN+ group were better at 0.5 and 2 kHz. Conclusions: Carhart notch or more appropriately the Carhart effect was observed at a wide range of frequencies, predominantly at 2 kHz. However, it is not an indicator of successful surgery. We identified preoperative audiological factors influencing BC improvement: 4 kHz BC improvement was significantly lower in case of preoperative Carhart notch or in presence of an AC--notch at 2 kHz. These findings should alert the clinician to a mixed hearing loss with preoperative sensorineural hearing loss (SNHL) or to a higher incidence of postoperative SNHL.
- Subjects
POLAND; EAR ossicle surgery; EAR surgery; PREOPERATIVE care; BONE conduction; CONFERENCES &; conventions; TREATMENT effectiveness; OTOSCLEROSIS; AUDIOMETRY; PREDICTION models; EVALUATION
- Publication
Journal of Hearing Science, 2022, Vol 12, Issue 1, p48
- ISSN
2083-389X
- Publication type
Article